Abstract A mechanism describing the synergistic effect of ultrasonic melt treatment (UST) and subsequent fast cooling on the refinement of primary Si particles in a hypereutectic Al−Si alloy was investigated by examining inoculant particles via high-resolution transmission electron microscopy, serial sectioning, and melt filtration. The application of UST activated non-wetting MgAl2O4 particles with diameters of ∼0.5 μm to nucleate the primary Si phase. The cavitation-enhanced wetting of MgAl2O4 particles caused the formation of the AlP phase at the MgAl2O4 interface, further improving the nucleation potential. The cavitation-enhanced wetting and dispersion of inclusions (such as MgAl2O4) also resulted in the refinement and de-agglomeration of AlP particles. The UST-induced changes to the inoculant particles ultimately increased their number density, and the observed effects became more pronounced after increasing the degree of undercooling up to 20 K, leading to enhanced refinement of primary Si particles at higher cooling rates (up to 102 K s−1).

中文翻译：

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超声熔体处理和快速冷却对过共晶铝硅合金中初生硅细化的协同作用

摘要 通过高分辨率透射电子显微镜、连续切片和连续切片检查孕育剂颗粒，研究了描述超声熔体处理 (UST) 和随后快速冷却对过共晶 Al-Si 合金中初生 Si 颗粒细化的协同作用的机制。熔体过滤。应用 UST 活化的非润湿性 MgAl2O4 颗粒（直径约为 0.5 μm）使初级 Si 相成核。MgAl2O4 颗粒的空化增强润湿导致在 MgAl2O4 界面形成 AlP 相，进一步提高了成核潜力。内含物（如 MgAl2O4）的空化增强润湿和分散也导致了 AlP 颗粒的细化和解聚。